adric22 wrote:But if you went with Panasonic cells, I don't see how you could go wrong.

If you are talking about the sort of Panasonic cells that Tesla uses I can see a very big problem if you don't also incorporate some sort of cooling system (but how?): they aren't as safe at high temperatures as the LiMn chemistry Nissan uses. Perhaps Panasonic also makes some cells using a chemistry that doesn't require cooling to be safe.

JeremyW wrote:No idea how long these aftermarket batteries would last, but I do know one thing:

You'd own the battery outright.

It's not always how long the battery will last before it dies though - sometimes you don't get the same performance either. I bought a couple of cheap batteries NB-3L batteries for my digital camera and have regretted it to this day. They're still plugging along, but even though they're both supposed to be rated higher mAh, the both of them together don't run the camera as long as the one Canon brand battery that is a fair bit older.

JeremyW wrote:No idea how long these aftermarket batteries would last, but I do know one thing:

You'd own the battery outright.

It's not always how long the battery will last before it dies though - sometimes you don't get the same performance either. I bought a couple of cheap batteries NB-3L batteries for my digital camera and have regretted it to this day. They're still plugging along, but even though they're both supposed to be rated higher mAh, the both of them together don't run the camera as long as the one Canon brand battery that is a fair bit older.

I've had opposite results replacing batteries for various items such as cordless phones, bicycle headlight systems, walkway lights, and of course 12V car batteries. You just need to take the time and source proper cells for the application, from respected manufacturers that give accurate specs. Usually this doesn't mean buying them "from a guy on Ebay".

Many consumer items with rechargeable batteries built-in, use rather cheap cells. I just got replacement cells for my wife's TENS unit, for one example and they are giving over twice the runtime as the originals did when they were new, and they are a limited self-discharge chemistry as well so will retain a charge over months of storage whereas the originals would fade in a couple of weeks.

This was discussed in another thread a while ago, although there was less urgency then. One of the things that came up was the proprietary nature of the battery controller and the VCM. Both of these computers must speak the same language for the pack replacement to work. One of the reasons for the lack of a 6 kW onboard charger upgrade was the new revision of the VCM, and other changes in control electronics in 2013 LEAFs, which would make the replacement cost prohibitive on older vehicles.

I like the effort around adding another 3.3 kW charger to the car, and keeping the same hardware. Interestingly, the OBC in the ActiveE consists of two 3.3 kW charger in parallel. So even OEMs can use this approach. Based on the old thread I mentioned above, the best way to approach pack replacement is to find a manufacturer willing to build cells with similar characteristics and identical form factor. Then reuse the existing hardware and computers to build a remanufactured pack. Depending on the condition of the cells pulled from the old pack, they could be likely re-sold for second-life applications.

The remaining questions here are: is it necessary to match the nominal capacity and the voltage curves of the original AESC cells? Will a battery controller be available for purchase and if not, can it be reverse-engineered?

IMO it's going to be much easier to augment the existing pack (like Enginer) than to replace existing modules.

The big issue with modifying the existing pack is that you'll have to find some cells that are compatible both electronically (operates in a 3.0-4.1V range, has similar impedance to the LEAF pack) and physically (easiest if you can fit pouch cells into an existing module so it's basically plug-and-play). Otherwise you're going to end up having to do a lot more hacking of the stock LEAF systems which will involve quite a bit of reverse engineering.

Alternatively, you can build any pack you like that fits into the trunk with the appropriate BMS, DC-DC inverter to tie into the existing HV lines and even piggy back off the stock AC feed for charging.

The only tricky part here is finding/programming the apropriate DC-DC inverter. I would also highly recommend tapping into the existing wiring a little bit more securely than the Enginer method - getting an extra M/F connector that you can plug in will let you plug your battery system in without leaving any trace of the system in the LEAF. Another benefit is that it should be possible to build a system that is easily removable - that way you only have to carry the extra weight around when you need the range.